Question

a Java code

Complete the provided code by adding a method named sum() to the LinkedList class. The sum() method should calculate the sum of all of the positive numbers stored in the linked list.

The input format is the number of items in the list, followed by each of the items, all separated by spaces. Construction of the linked list is provided in the template below. The output should print the sum of the positive values in the list.

For example, the input

4 5 9 -3 2

will produce the output

The sum of the positive items in the list is: 16

(because 5 + 9 + 2 = 16).

import java.util.*;

/***************************************************
* COMP 2140 Lab 4
*
* Simple linked list:
* Add up the positive values stored in a linked list.
***************************************************/

public class Lab4 {

public static void main( String[] args ) {
       Scanner keyboard;
       int listSize;
       LinkedList myList;

       keyboard = new Scanner( System.in );

       //get number of values in list
listSize = keyboard.nextInt();

       //create list
       myList = new LinkedList();

       //fill list
       for (int i=0; i<listSize; i++){
myList.insert(keyboard.nextInt());
       }

       keyboard.close();

       //print results
       System.out.println( "The sum of the positive items in the list is: " + myList.sum() );

} // end main

} // end class Lab4

//=====================================================
// LinkedList class
//
// An ordinary linked list containing ints.
// The list consists of just a pointer (top)
// to the first node in the list.
//=====================================================
class LinkedList {

//================================================
// Node class
//
// A node in the linked list.
// Note that it is inside the LinkedList class.
//
// The usual accessors and mutators (getters and
// setters) are unnecessary. You can directly access
// the instance members "item" and "next" in any
// node that you have a pointer to without using
// accessors or mutators anywhere in the
// LinkedList class. Why? Because item and next
// are declared public in the private Node class
// inside the LinkedList class.
//================================================
private class Node {
       public int item;
       public Node next;

       // Node constructor
       public Node( int newItem, Node newNext ) {
       item = newItem;
       next = newNext;
       }

} // end class Node

/********* Returning to class LinkedList ************/

private Node top; // A pointer to the first node in
// the list (when it's not empty)

/******************************************
*
* LinkedList constructor
*
* Creates an empty LinkedList.
*
******************************************/
public LinkedList( ) {
       top = null;
}

/******************************************
*
* insert
*
* It is passed a new value to add to the list.
*
* It inserts a new node containing newItem
* at the front of the list.
*
* It does NOT check for duplicates ---
* duplicate values are allowed.
*
******************************************/
public void insert( int newItem ) {
       top = new Node( newItem, top );
}
  
public int sum(){
if(next != null){
if(item > 0){
int sum += item ;
  
}
  
}
return sum;

}

} // end class LinkedList

Answer 1

JAVA PROGRAM

import java.util.*;

public class Lab4 {
/***************************************************
* COMP 2140 Lab 4
*
* Simple linked list:
* Add up the positive values stored in a linked list.
***************************************************/
public static void main( String[] args ) {
Scanner keyboard;
int listSize;
LinkedList myList;

keyboard = new Scanner( System.in );

//get number of values in list
listSize = keyboard.nextInt();

//create list
myList = new LinkedList();

//fill list
for (int i=0; i<listSize; i++){
myList.insert(keyboard.nextInt());
}

keyboard.close();

//print results
System.out.println( "The sum of the positive items in the list is: " + myList.sum() );

} // end main

} // end class Lab4

//=====================================================
// LinkedList class
//
// An ordinary linked list containing ints.
// The list consists of just a pointer (top)
// to the first node in the list.
//=====================================================
class LinkedList {
//================================================
// Node class
//
// A node in the linked list.
// Note that it is inside the LinkedList class.
//
// The usual accessors and mutators (getters and
// setters) are unnecessary. You can directly access
// the instance members "item" and "next" in any
// node that you have a pointer to without using
// accessors or mutators anywhere in the
// LinkedList class. Why? Because item and next
// are declared public in the private Node class
// inside the LinkedList class.
//================================================
private class Node {
public int item;
public Node next;

public Node( int newItem, Node newNext ) {
item = newItem;
next = newNext;
}

}// end class Node

/********* Returning to class LinkedList ************/

private Node top; // A pointer to the first node in
// the list (when it's not empty)

/******************************************
*
* LinkedList constructor
*
* Creates an empty LinkedList.
*
******************************************/
public LinkedList( ) {
top = null;
}

/******************************************
*
* insert
*
* It is passed a new value to add to the list.
*
* It inserts a new node containing newItem
* at the front of the list.
*
* It does NOT check for duplicates ---
* duplicate values are allowed.
*
******************************************/
public void insert( int newItem ) {
top = new Node( newItem, top );
}

public int sum(){
int sum=0;
while(top != null){
if(top.item > 0)
sum += top.item;
top=top.next;
}
return sum;
}// end class LinkedList

}

OUTPUT

S S 9 1 2 6 7 8 : 2 The sum of the positive items in the list is: 16